It also comes as legislation proposed last week to set FAA policy for the next six years would continue a prohibition on new lithium restrictions in the U.S. that are stricter than those adopted by the United Nations’ aviation arm, the International Civil Aviation Organization.

Airline ban

While most passenger airlines last year banned bulk shipments of lithium rechargeable batteries, some U.S. and foreign airlines continue to carry them and there is no legal restriction.

Cargo companies such as United Parcel Service Inc. and FedEx Corp. have not followed the passenger carriers in banning the shipments. Both companies are working on technology to limit the potential for battery fires.

The Air Line Pilots Association, the largest flight-crew union in North America, separately on Tuesday called on Congress to give the FAA more power to regulate lithium shipments.

“Lithium batteries pose a significant safety threat to air transportation,” Mark Rogers, head of ALPA’s dangerous goods committee, said at a briefing. “It’s important that the U.S. not delegate its responsibility as a sovereign nation to an international body. The U.S. should set the example and lead international efforts.”

Voluntary regulations

Because of language in a 2012 bill, FAA and the Pipeline and Hazardous Materials Safety Administration, which jointly regulate how hazardous materials may be carried on airline flights, have had to resort to voluntary recommendations instead of regulatory action in spite of growing evidence implicating the batteries.

Aircraft manufacturers Boeing Co. and Airbus Group SE warned carriers last year against carrying the batteries as cargo until new protections are developed. While it can’t impose the actions itself, the FAA in October said it favored a ban on shipments aboard passenger flights until ne

w packaging can prevent fires and urged ICAO to take the same position.

An ICAO panel in October rejected such a ban. Another ICAO advisory panel on Jan. 28 took the opposite position, saying shipments should stop until new packaging is developed. The ICAO Council must decide the issue later this year.

Asiana crash

Three cargo aircraft accidents, two of them fatal, have been linked to lithium-based batteries that caught fire, according to the NTSB and other accident investigation agencies.

The NTSB, which can only recommend regulatory changes, said its investigation of a 2011 crash of an Asiana Airlines in waters off South Korea led it to conclude the risk of a fire from battery cargo warranted action. It urged the Pipeline and Hazardous Materials Safety Administration to impose restrictions on the placement and volume of lithium battery cargo.

“The NTSB strongly believes the circumstances and findings in the Asiana Flight 991 accident show the need for new cargo segregation and loading density requirements,” the NTSB said in a news release.

Delta, United

While many large passenger carriers, including United Continental Holdings Inc. and Delta Air Lines Inc., said last year they won’t ship the power packs as cargo until new safety measures are developed, such shipments are legal and some carriers continue to handle them. About 26 million people a year fly to and from the U.S. on foreign carriers that allow lithium shipments, according to the FAA.

The FAA’s advisory Tuesday doesn’t apply to batteries contained devices carried by passengers and crew members.

The agency said it “strongly recommends” that passenger and cargo airlines review their battery shipments as more evidence emerges about the threat. Not only will the power units explode, but they also can emit smoke and gases that will spread to the rest of the aircraft, the FAA said in the alert.

“The number of cells necessary to produce this condition is small and can occur with just a few packages,” the agency said in the alert.

Airlines should review the types of batteries they carry, the reliability of the companies shipping them and their employee training, according to the agency.

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